1. Field of the Invention
The present invention relates to a high voltage transformer, and more particularly, to a high voltage transformer of a microwave oven having a structure for radiating heat efficiently.
2. Description of the Prior Art
Generally, a high voltage transformer is a device for generating a certain degree of high voltage with a commonly used alternating current of 100V/220V input thereto. The high voltage transformer is essentially employed into home appliances such as a microwave oven which generates microwave to cook the foods, or the like, in order to supply the high voltage thereto.
FIG. 1 is a perspective view showing a conventional high voltage transformer. As shown, the conventional high voltage transformer is constructed in such a manner that a plurality of E-shaped or I-shaped iron plates 1a are fixed together one after another so as to form a rectangular core 1, and a coil 2 is wound many times at the center thereof.
An input terminal 3 is electrically connected with a side of the coil 2, while an output terminal 4 is electrically connected with the other side thereof. Therefore, when the commonly used alternating current (hereinafter AC) generally of 110V or 220V is input into the high voltage transformer through the input terminal 3, the high voltage transformer converts the AC power into the high voltage of predetermined value according to the winding ratio of the coil 2, and then outputs the high voltage through the output terminal 4.
In general, the high voltage output from the high voltage transformer is 2100.about.2400VAC. The high voltage is supplied to the components of the microwave oven such as a magnetron (not shown), a high voltage condenser (not shown), and a high voltage diode (not shown) to generate a microwave of a predetermined value of frequency.
When the conventional high voltage transformer operates, it generates a great amount of heat due to an inner resistance thereof, and the heat is radiated outside through the surface of the core 1.
In this situation, the inner resistance of the high voltage transformer is directly proportional to a length of the coil, while the inner resistance is inversely proportional to the sectional area of the coil. The coil should be long in order to generate the high voltage, so the inner resistance increases and thereby the transformer generates excessive heat.
Therefore, it is recommended that the circumference of the core 1 should be as large as possible so that the surface contacted with the air is large enough to keep the temperature thereof within a range of safety.
Additionally, for the efficient heat radiation, a blowing fan (not shown) is installed near the high voltage transformer. The blowing fan blows outside air in force to cool the high voltage transformer.
However, since the conventional high voltage transformer has to be large so as to radiate its own heat, the volume and the weight thereof are also quite large. This causes an inconvenience to a user who has to handle the high voltage transformer of generally 3.5.about.5.5 kg. Also, the manufacturing cost increases. Therefore, there is a great demand for the small and light high voltage transformer, which will solve the problems of the inconvenience and the large sum of manufacturing cost.